Body panels of a motor vehicle, including the vehicle's glazing units, must satisfy numerous design criteria. Among the most significant criteria arc suitability for assembly, especially initial assembly in a commercial volume assembly line and repair or retrofit assembly. Another significant criterion is energy containment, with controlled deformation of body panels generally being relied upon for significant contribution in this regard. The polyvinyl butyral (PVB) laminate layer in motor vehicle windshields, for example, provides good energy absorption in the course of fracture and deformation. Motor vehicle body panels also must meet aesthetic design criteria, providing a smooth and flush outer surface. This has been a long-term design objective both for aesthetic reasons and to provide functional improvements, such as improved fuel economy by reduced aerodynamic drag.
Motor vehicle glazing units having a moveably mounted glazing pane, most notably the side windows of a vehicle, have generally employed a tempered glass pane sliding up and down in a pair of U-shaped run channels. Such designs, while being well suited to modern motor vehicle assembly operations, can compromise the aesthetic qualities of the vehicle design due to their recessed or lack of flushness with the surrounding window frame. In addition, it would be desirable to increase the energy absorption of such glazing units.
Bilaminate and trilaminate glazings have been suggested for use as moveably mounted panes in motor vehicles. In U.S. Pat. No. 4,823,511 to Herliczek et al, laminated glazing panes are suggested having a three-sided edge support molded along the vertical edges. The edge support is three-sided in the sense that it wraps around the edge of the glass pane, contacting the outboard surface, the peripheral side edge and the inboard surface of the pane. The edge support of the Herliczek patent extends into run channels in the window frame and is captured therein to provide improved retention strength. The cross-sectional configuration of the edge support may, for example, be T-shaped, L-shaped or rounded, in each case being received into a correspondingly configured run channel in the window frame. Such three-sided edge support designs are disadvantageous in that they prevent a smooth flush window appearance. Specifically, the portion of the edge support which wraps around the outboard surface of the glazing pane presents an undesirable interruption of the otherwise smooth glazing pane surface. In addition, the edge support presents significant assembly disadvantages. Specifically, the T-shaped and L-shaped configurations must be top loaded or bottom loaded into the vertical run channels. While the rounded configurations having no T-shaped or L-shaped projections may be more suitable for assembly operations, being received in some cases laterally into the run channels, they may for that reason also provide less improvement in window pane retention. Energy absorption by fracture and deformation of a laminated glazing pane is dependent, of course, on suitable edge retention.
It is an object of the present invention to provide motor vehicle glazing units having moveably mounted glazing panes which provide good energy containment properties. It is a further object of at least certain preferred embodiments of the invention, to provide motor vehicle glazing units having such energy containment properties while still providing good aesthetic and design-for-assembly characteristics. Additional objects and advantages of the invention and/or of at least certain preferred embodiments will be readily understood from the following disclosure and detailed description.